The invention relates to a continuously operating centrifugal separator having hydraulically controlled outlet valves for control of the concentration of suspended solids in the concentrated phase produced by the separator.
A centrifugal separator of this type is known, for example, from French Pat. No. 1,554,226, the outlet valves of the passages being operated in accordance with the concentration of the discharged solids. In order to prevent clogging of the outlet valves and the associated danger of the sludging up of the separator or of drum imbalance in the event of an elevated content of solids, the outlet valves have to be enlarged, and in the case of a reduced content of solids they have to be made smaller, so that the desired concentration of the solids will remain constant. In order to avoid to the greatest possible extent the clogging of the outlet passages leading to the valves, the cross section of the passages must be designed for a maximum content of solids.
In the above-cited French Patent, the operation of the outlet valves for the concentrate must be performed through a hydraulic, pneumatic or electromagnetic, controllable closing device disposed in the hollow spindle of the centrifuge, which opens the discharge orifice of the outlet valves as the concentration increases and closes it as the concentration decreases. The regulation of the closing device is performed, for example, in conjunction with a viscosity measuring means provided in the concentrate outlet.
The disadvantage of this closing device is that, on the one hand, its construction is very expensive, and on the other hand the outlet valves can be sealed off only imperfectly, and fine regulation is not possible, since the valves can only open all the way or close all the way. In addition, the closing device must be operated in the outer reach of the paring chamber inside of the solids ring. The disassembly of the valves with the outlet tubes or of the closing device in case of trouble is very complicated since they are disposed in the lower part of the separator and necessitate a complete disassembly of the drum or centrifuge.